I. Field of the Invention
The present invention relates to a frame and cover assembly for a mechanical stapler.
II. Background of the Invention
There are a number of support frame and cover assemblies used with conventional staplers. For example, U.S. Pat. No. 4,119,258 to Ewig, Jr. discloses a frame consisting of two spaced parallel side walls formed of a high density polymer. The interior of the side walls have webs which cooperate to define structural support features for the internal components of the stapler. The support features include an internally directed flange which cooperates with a similar flange on the other half of the housing and the side walls to define a cavity, as well as a boxlike enclosure formed by two other flanges. The stapler contains a hammer that is slidable within the box-like enclosure and a spring, a portion of which fits within the cavity. Ewig, Jr. discloses that the high density polymer stapler frame is particularly advantageous because of the difficulty in producing a lowcost, light-weight metal stapler.
Frame and cover assemblies also have been made using a combination of metal and plastic components. U.S. Pat. No. 3,786,978 to Manganaro discloses an electromagnetic stapler having a pair of metal frame members comprising a plurality of wall surfaces for enveloping the stapler components. A pair of the wall surfaces are bent to support a base plate beneath the bumper or plunger element. The frames include apertures for receiving bolts to secure various stapler components to the frames. The stapler also includes a front cover plate secured to the frames. Further, a pair of insulating covers are fixed to each other about the frame members. U.S. Pat. No. 2,769,174 to Libert is similar to Manganaro and includes a metal frame member that provides a housing and a support for other elements of the stapler. This reference includes a front cover plate, which is affixed at the sides of the frame. Neither Libert or Manganaro disclose surfaces, such as the flanges in Ewig, Jr., which are capable of providing structural support to the internal components of the stapler. In addition, both of these references require a separate cover plate on the front portion of the stapler, thus complicating the manufacture and increasing the cost of production of the stapler.
As is apparent from consideration of the noted conventional devices, it has been desirable to provide frame members for mechanical staplers which are formed of metal, since such devices are more durable and less susceptible to fatigue. However, as evidenced by Ewig, Jr. the cost of production of such frames and the overall effect on the weight of the stapler have outweighed the obvious benefits of metal frame members. Hence, the trend is to produce frame members formed of plastic, which are also generally much easier to assemble.
It is, therefore, a principal objective of the present invention to provide an economically manufactured stapler frame and cover assembly that employs a metal frame to give effective structural support to the internal stapler components.
It is an additional objective of the present invention to provide a frame and cover assembly having a reduced number of parts that is correspondingly easy to assemble.
It is another objective of the present invention to provide a simple and economical method of forming a stapler frame and cover assembly.
Additional objectives and advantages of the present invention will be set forth in part in the description that follows and in part will be obvious from the description or may be learned by practice of the invention. The objectives and advantages of the invention may be realized and obtained by the methods and apparatus particulary pointed out in the appended claims.